For several years, one of the hottest ethical questions in biotechnology was whether it would be a good idea to wipe out the disease-spreading mosquito species using a radical technique known as a gene drive. It's been a hypothetical debate, until the recent announcement that the technique has been tested in the lab and could be ready for use soon.

Now that it's almost ready, the debate is no longer hypothetical, and we must add a question to it, "Is it ethical not to wipe out these mosquitos, as soon as possible."

Naturally, everybody is very wary of wiping out a species using genetic engineering. The way this gene drive works, altering the term line of creatures so that they only have male offspring, and those males only have male offspring as well, is downright creepy. It conjures up all sorts of fears of "meddling with forces we don't understand" and "tampering with the very nature of life itself" -- the two credos of every good mad scientist. It's easy to wonder what could go wrong, and ask, "what's the worst that could happen?" in a very sarcastic way.

That's not an unreasonable question to ask. On the other side, there are some factors to reduce the fear:

• Humans have wiped out thousands of species, and we're going to wipe out thousands more. It's a terrible thing, but it has not caused vast ecological catastrophe.
• Only a few species (out of 3,500 different kinds) would be targeted. The mosquito would definitely not go away, just the ones that carry malaria an dengue fever and a few other diseases.
• These species are actually invasive in most of the areas they exist. If we knew how, would would eliminate them only where they have invaded with minimal risk of ecological harm. (In fact we would be repairing past ecological damage.) However, the loss of the species in their original territories present even less ecological risk than one might first imagine.
• We would sequence the destroyed creatures, or possibly keep captive colonies of them in case we learned we needed to re-introduce them back in their native area. Or we might be able to introduce a similar (non-human-harming) mosquito in that area to replace their ecological role.

But:

• While the spread of the gene drive to other species is extremely unlikely, people can't rule it out entirely.
• It's also not impossible that the parasites might evolve to move to another host. They do that sort of thing.
• Other things could happen we haven't thought of. But other fixes might be possible that we haven't thought of as well.

The natural reaction to what I've written above would be to say, "Let's examine this carefully, and do a lot of deliberation before going forward with something like this, if we do it at all."

But there's a big problem. Estimates suggest that around 750,000 people die every year from mosquito born diseases, and as many as 500 million suffer from them. 500,000 die from malaria each year with 212 million infected. I've seen larger estimates, but this number is enough.

500,000 per year. 1,400 a day. Several while you read this article. Painfully.

While the gene drive would not be instant, over time the result is the same. If we delay deploying this one year, 750,000 will die nasty deaths. Wait 8 years and you have the losses of the Jewish people in the holocaust. Wait 28 days and you have all the U.S. deaths in Vietnam. Wait just over 2 days and the World Trade Center falls.

So how long is it prudent to wait? We don't know who they are, but these deaths going forward are on our hands, or the hands of those able to apply the technique and those who control them. If we act to slow it down, they are on our hands.

So while one might understand all the principles of prudence listed above, is there a limit to how much caution should be applied when the alternative, the true "what's the worst that could happen?" is the certainty of millions of deaths. It seems very likely that the "worst that could happen" would be to do nothing.

Alternatives

However, it gets more complicated when it is revealed that there may be alternative ways to deal with these diseases than the wiping out of these few species of mosquito. For some time, insect population control has been done by releasing sterilized males into an area. There are now promising ways to massively scale that up. There may be ways to wipe out the parasites that actually cause the diseases instead of the mosquitoes. There are potential gene drive variants that aren't so dramatic in their effect as a quick-extermination. If we had such a technique at our disposal today, we would probably select to use it. It's a likely prediction that some alternative to the gene drive, without its potential complications, will arise, but it is unknown when.

Does this alter the equation? Is prudence the answer?

Mosquito borne diseases are not the largest external killers. Pneumonia, AIDS, waterborne diseases and of course, car crashes kill even more. As readers know, we're working on the car crashes. But the mosquito borne diseases are now the leading killer we can do something about today, and cheaply.

Dare we do it? Dare we not?